Hydroxylamine derivatives

ABSTRACT

The invention concerns hydroxylamine derivatives of the formula I ##STR1## wherein R 4  is hydrogen, carbamoyl, (1-4C)alkyl, (2-5C)alkanoyl, N-(1-4C)alkylcarbamoyl, N,N-di-(1-4C)alkylcarbamoyl, benzoyl or phenylsulphonyl; 
     R 5  includes hydrogen, (1-4C)alkyl and (2-5C)alkanoyl; 
     R 6  is hydrogen, (1-4C)alkyl, phenyl or phenyl-(1-4C)alkyl; 
     R 7  is hydrogen or (1-4C)alkyl; 
     Ar 1  is phenylene; 
     A 1  is a direct link to X 1 , or A 1  is (1-4C)alkylene; 
     X 1  is oxy, thio, sulphinyl or sulphonyl; 
     Ar 2  is phenylene, pyridinediyl, pyrimidinediyl, thiophenediyl, furandiyl, thiazolediyl, oxazolediyl, thiadiazolediyl or oxadiazolediyl; 
     R 1  is (1-4C)alkyl, (3-4C)alkenyl or (3-4C)alkynyl; and 
     R 2  and R 3  together form a group of the formula --A 2  --X 2  --A 3  -- which together with the carbon atom to which A 2  and A 3  are attached define a ring having 5 or 6 ring atoms, wherein each of A 2  and A 3  is independently (1-3C)alkylene and X 2  is oxy, thio, sulphinyl, sulphonyl or imino; 
     or a pharmaceutically-acceptable salt thereof; 
     processes for their manufacture; pharmaceutical compositions containing them and their use as 5-lipoxygenase inhibitors.

This invention concerns hydroxylamine derivatives and more particularly hydroxylamine derivatives which are inhibitors of the enzyme 5-lipoxygenase (hereinafter referred to as 5-LO). The invention also concerns processes for the manufacture of said hydroxylamine derivatives and novel pharmaceutical compositions containing them. Also included in the invention is the use of said hydroxylamine derivatives in the treatment of various inflammatory and/or allergic diseases in which the direct or indirect products of 5-LO catalysed oxidation of arachidonic acid are involved, and the production of new medicaments for such use.

As stated above the hydroxylamine derivatives described hereinafter are inhibitors of 5-LO, which enzyme is known to be involved in catalysing the oxidation of arachidonic acid to give rise via a cascade process to the physiologically active leukotrienes such as leukotriene B₄ (LTB₄) and the peptido-lipid leukotrienes such as leukotriene C₄ (LTC₄) and leukotriene D₄ (LTD₄) and various metabolites.

The biosynthetic relationship and physiological properties of the leukotrienes are summarised by G. W. Taylor and S. R. Clarke in Trends in Pharmacological Sciences, 1986, 7, 100-103. The leukotrienes and their metabolites have been implicated in the production and development of various inflammatory and allergic diseases such as inflammation of the joints (especially rheumatoid arthritis, osteoarthritis and gout), inflammation of the gastrointestinal tract (especially inflammatory bowel disease, ulcerative colitis and gastritis), skin disease (especially psoriasis, eczema and dermatitis) and respiratory disease (especially asthma, bronchitis and allergic rhinitis), and in the production and development of various cardiovascular and cerebrovascular disorders such as myocardial infarction, angina and peripheral vascular disease. In addition the leukotrienes are mediators of inflammatory diseases by virtue of their ability to modulate lymphocyte and leukocyte function. Other physiologically active metabolites of arachidonic acid, such as the prostaglandins and thromboxanes, arise via the action of the enzyme cyclooxygenase on arachidonic acid.

It is disclosed in European Patent Application Nos. 0375404 A2 and 0385662 A2 that certain heterocyclic derivatives possess inhibitory properties against 5-LO. Furthermore European Patent Applications Nos. 0409413 and 0420511 are also concerned with heterocyclic derivatives which possess inhibitory properties against 5-LO. We have now discovered that certain hydroxylamine derivatives which possess some structural features which are similar to those of the compounds disclosed in the above-mentioned applications but which possess other structural features, in particular hydroxylamine groups, which were not envisaged in those earlier applications are effective inhibitors of the enzyme 5-LO and thus of leukotriene biosyntheses. Thus such compounds are of value as therapeutic agents in the treatment of, for example, allergic conditions, psoriasis, asthma, cardiovascular and cerebrovascular disorders, and/or inflammatory and arthritic conditions, mediated alone or in part by one or more leukotrienes.

According to the invention there is provided a hydroxylamine derivative of the formula I ##STR2## wherein R⁴ is hydrogen, carbamoyl, (1-4C)alkyl, (2-5C)alkanoyl, N-(1-4C)alkylcarbamoyl, N,N-di-(1-4C)alkylcarbamoyl, benzoyl or phenylsulphonyl and wherein the benzoyl or phenylsulphonyl group may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, (1-4C)alkyl and (1-4C)alkoxy;

R⁵ is hydrogen, (1-4C)alkyl, (3-4C)alkenyl, (3-4C)alkynyl, (2-5C)alkanoyl, halogeno-(2-4C)alkyl, hydroxy-(2-4C)alkyl, (1-4C)alkoxy-(2-4C)alkyl, amino-(2-4C)alkyl, (1-4C)alkylamino-(2-4C)alkyl, di-(1-4C)alkylamino-(2-4C)alkyl, (1-4C)alkylthio-(2-4C)alkyl, (1-4C)alkylsulphinyl-(2-4C)alkyl, (1-4C)alkylsulphonyl-(2-4C)alkyl, cyano-(1-4C)alkyl, carboxy-(1-4C)alkyl, (1-4C)alkoxycarbonyl-(1-4C)alkyl, carbamoyl-(1-4C)alkyl, N-(1-4C)alkylcarbamoyl-(1-4C)alkyl, N,N-di-(1-4C)alkylcarbamoyl-(1-4C)alkyl or phenyl-(1-4C)alkyl and wherein the phenyl-(1-4C)alkyl group may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, (1-4C)alkyl and (1-4C)alkoxy;

R⁶ is hydrogen, (1-4C)alkyl, phenyl or phenyl-(1-4C)alkyl and wherein each phenyl group may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, (1-4C)alkyl and (1-4C)alkoxy;

R⁷ is hydrogen or (1-4C)alkyl;

Ar¹ is phenylene which may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, (1-4C)alkyl and (1-4C)alkoxy;

or

R⁶ is linked to Ar¹ ortho to the --C(R6)(R⁷)-- group and defines an ethylene, propylene, 1-methylpropylene or vinylene group, a group of the formula

    --CH═CH--X.sup.3 --

wherein

X³ is oxy or thio, or a group of the formula

    --(CH.sub.2).sub.n --X.sup.3 --

wherein

n is 1 or 2, X³ is oxy or thio and one of the --CH₂ -- groups may optionally be replaced by a --CH(Me)-- or --C(Me)₂ -- group;

A¹ is a direct link to X¹, or A¹ is (1-4C)alkylene;

X¹ is oxy, thio, sulphinyl or sulphonyl;

Ar² is phenylene, pyridinediyl, pyrimidinediyl, thiophenediyl, furandiyl, thiazolediyl, oxazolediyl, thiadiazolediyl or oxadiazolediyl which may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, (1-4C)alkyl and (1-4C)alkoxy; R¹ is (1-4C)alkyl, (3-4C)alkenyl or (3-4C)alkynyl; and

R² and R³ together form a group of the formula --A² --X² --A³ -- which together with the carbon atom to which A² and A³ are attached define a ring having 5 or 6 ring atoms, wherein each of A² and A³ is independently (1-3C)alkylene and X² is oxy, thio, sulphinyl, sulphonyl or imino, and which ring may optionally bear one or two substituents selected from hydroxy, (1-4C)alkyl and (1-4C)alkoxy;

or wherein

R¹ and R² together form a group of the formula --A² --X² --A³ -- which together with the oxygen atom to which A² is attached and with the carbon atom to which A³ is attached define a ring having 5 or 6 ring atoms, wherein A² and A³, which may be the same or different, each is (1-3C)alkylene and X² is oxy, thio, sulphinyl or sulphonyl and which ring may bear one, two or three (1-4C)alkyl substituents, and wherein R³ is (1-4C)alkyl, (2-4C)alkenyl or (2-4C)alkynyl; or a pharmaceutically-acceptable salt thereof.

In a further aspect of the invention there is provided a hydroxylamine derivative of the formula I wherein R⁴ is hydrogen, carbamoyl, (1-4C)alkyl, (2-5C)alkanoyl, N-(1-4C)alkylcarbamoyl, N,N-di-(1-4C)alkylcarbamoyl, benzoyl or phenylsulphonyl and wherein the benzoyl or phenylsulphonyl group may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, (1-4C)alkyl and (1-4C)alkoxy;

R⁵ is hydrogen, (1-4C)alkyl, (2-5C)alkanoyl, halogeno-(2-4C)alkyl, hydroxy-(2-4C)alkyl, amino-(2-4C)alkyl, (1-4C)alkylamino-(2-4C)alkyl, di-(1-4C)alkylamino-(2-4C)alkyl, (1-4C)alkylthio-(2-4C)alkyl, (1-4C)alkylsulphinyl-(2-4C)alkyl, (1-4C)alkylsulphonyl-(2-4C)alkyl, cyano-(1-4C)alkyl, carboxy-(1-4C)alkyl, (1-4C)alkoxycarbonyl(1-4C}alkyl, carbamoyl-(1-4C)alkyl, N-(1-4C)alkylcarbamoyl(1-4C)alkyl, N,N-di-(1-4C)alkylcarbamoyl-(1-4C)alkyl or phenyl-(1-4C)alkyl and wherein the phenyl-(1-4C)alkyl group may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, (1-4C)alkyl and (1-4C)alkoxy;

R⁶ is hydrogen, (1-4C)alkyl, phenyl or phenyl-(1-4C)alkyl and wherein each phenyl group may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, (1-4C)alkyl and (1-4C)alkoxy;

R⁷ is hydrogen or (1-4C)alkyl;

Ar¹ is phenylene which may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, (1-4C)alkyl and (1-4C)alkoxy;

A¹ is a direct link to X¹, or A¹ is (1-4C)alkylene;

X¹ is oxy, thio, sulphinyl or sulphonyl;

Ar² is phenylene, pyridinediyl, pyrimidinediyl, thiophenediyl or furandiyl which may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, (1-4C)alkyl and (1-4C)alkoxy;

R¹ is (1-4C)alkyl, (3-4C)alkenyl or (3-4C)alkynyl; and

R² and 113 together form a group of the formula --A² --X² --A³ -- which together with the carbon atom to which A² and A³ are attached define a ring having 5 or 6 ring atoms, wherein each of A² and A³ is independently (1-3C)alkylene and X² is oxy, thio, sulphinyl, sulphonyl or imino, and which ring may optionally bear one or two substituents selected from hydroxy, (1-4C)alkyl and (1-4C)alkoxy;

or a pharmaceutically-acceptable salt thereof.

The chemical formulae referred to herein by Roman numerals are set out for convenience on a separate sheet hereinafter.

In this specification the generic term "alkyl" includes both straight-chain and branched-chain alkyl groups. However references to individual alkyl groups such as "propyl" are specific for the straight-chain version only and references to individual branched-chain alkyl groups such as "isopropyl" are specific for the branched-chain version only. An analogous convention applies to other generic terms.

It is to be understood that, insofar as certain of the compounds of the formula I defined above may exhibit the phenomenon of tautomerism and any formula drawing presented herein may represent only one of the possible tautomeric forms, the invention includes in its definition any tautomeric form of a compound of the formula I which possesses the property of inhibiting 5-LO and is not to be limited merely to any one tautomeric form utilised within the formulae drawings.

It is further to be understood that, insofar as certain of the compounds of formula I defined above may exist in optically active or racemic forms by virtue of one or more asymmetric carbon atoms, the invention includes in its definition any such optically active or racemic form which possesses the property of inhibiting 5-LO. The synthesis of optically active forms may be carried out by standard techniques of organic chemistry well known in the art, for example by synthesis from optically active starting materials or by resolution of a racemic form.

Suitable values for the generic terms referred to above include those set out below.

A suitable value for R⁴, R⁵, R⁶ or R⁷ when it is (1-4C)alkyl is, for example, methyl, ethyl, propyl, isopropyl or butyl; and for R⁴ or R⁵ when it is (2-5C)alkanoyl is, for example, acetyl, propionyl, butyryl or pivaloyl.

A suitable value for R⁴ when it is N-(1-4C)alkylcarbamoyl is, for example, N-methylcarbamoyl, N-ethylcarbamoyl or N-propylcarbamoyl; and when it is N,N-di-(1-4C)alkylcarbamoyl is, for example, N,N-dimethylcarbamoyl, N-ethyl-N-methylcarbamoyl or N-N-dipropylcarbamoyl.

A suitable value for R⁵ or R⁶ when it is phenyl-(1-4C)alkyl is, for example, benzyl, phenethyl or 3-phenylpropyl.

Suitable values for substituents which may be present when R⁴, R⁵ or R⁶ is benzoyl, phenylsulphonyl phenyl or phenyl-(1-4C)alkyl, or for substituents on Ar¹ or Ar² include, for example:

    ______________________________________                                         for halogeno:   fluoro, chloro and bromo;                                      for (1-4C) alkyl:                                                                              methyl, ethyl, propyl and                                                      isopropyl;                                                     for (1-4C) alkoxy:                                                                             methoxy, ethoxy, propoxy and                                                   isopropoxy.                                                    ______________________________________                                    

A suitable value for R⁵ when it is (3-4C)alkenyl is, for example, allyl, 2-butenyl or 3-butenyl; when it is (3-4C)alkynyl is, for example, 2-propynyl or 2-butynyl; when it is halogeno-(2-4C)alkyl is, for example, 2-fluoroethyl, 2-chloroethyl, 2-bromoethyl, 3-fluoropropyl or 3-chloropropyl; when it is hydroxy-(2-4C)alkyl is, for example, 2-hydroxyethyl or 3-hydroxypropyl;

when it is (1-4C)alkoxy-(2-4C)alkyl is, for example, 2-methoxyethyl, 2-ethoxyethyl or 3-methoxypropyl;

when it is amino-(2-4C)alkyl is, for example, 2-aminoethyl or 3-aminopropyl; when it is (1-4C)alkylamino-(2-4C)alkyl is, for example, 2-methylaminoethyl, 2-ethylaminoethyl, 2-propylaminoethyl, 3-methylaminopropyl or 3-ethylaminopropyl; when it is di-(1-4C)alkylamino-(2-4C)alkyl is, for example, 2-dimethylaminoethyl, 2-diethylaminoethyl, 3-dimethylaminopropyl or 3-diethylaminopropyl; when it is (1-4C)alkylthio-(2-4C)alkyl is, for example, 2-methylthioethyl, 2-ethylthioethyl, 3-methylthiopropyl or 3-ethylthiopropyl;

when it is (1-4C)alkylsulphinyl-(2-4C)alkyl is, for example, 2-methylsulphinylethyl, 2-ethylsulphinylethyl, 3-methylsulphinylpropyl or 3-ethylsulphinylpropyl;

when it is (1-4C)alkylsulphonyl-(2-4C)alkyl is, for example, 2-methylsulphonylethyl, 2-ethylsulphonylethyl, 3-methysulphonylpropyl or 3-ethylsulphonylpropyl; when it is cyano-(1-4C)alkyl is, for example, cyanomethyl, 1-cyanoethyl, 2-cyanoethyl, 2-cyanoprop-2-yl or 3-cyanopropyl; when it carboxy-(1-4C)alkyl is, for example, carboxymethyl, 1-carboxyethyl, 2-carboxyethyl, 2-carboxyprop-2-yl or 3-carboxypropyl; when it is (1-4C)alkoxycarbonyl-(1-4C)alkyl is, for example, methoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl, tert-butoxycarbonylmethyl, 1-methoxycarbonylethyl, 1 -ethoxycarbonylethyl, 2 -methoxycarbonylethyl, 2-ethoxycarbonylethyl, 2-methoxycarbonylprop-2-yl, 2-ethoxycarbonylprop-2-yl, 3-methoxycarbonylpropyl or 3-ethoxycarbonylpropyl; when it is carbamoyl-(1-4C)alkyl is, for example, carbamoylmethyl, 1 -carbamoylethyl, 2-carbamoylethyl, 2-carbamoylprop-2-yl or 3-carbamoylpropyl; when it is N-(1-4C)alkylcarbamoyl-(1-4C)alkyl is, for example, N-methylcarbamoylmethyl, N-ethylcarbamoylmethyl, 1-(N-methylcarbamoyl)ethyl, 1-(N-ethylcarbamoyl)ethyl, 2-(N-methylcarbamoyl)ethyl, 2-(N-ethylcarbamoyl)ethyl, 2-(N-methylcarbamoyl)prop-2-yl, 2-(N-ethylcarbamoyl)prop-2-yl, 3-(N-methylcarbamoyl)propyl or 3-(N-ethylcarbamoyl)propyl; and when it is N,N-di-(1-4C)alkylcarbamoyl-(1-4C)alkyl is, for example, N,N-dimethylcarbamoylmethyl, N,N-diethylcarbamoylmethyl, 1-(N,N-dimethylcarbamoyl)ethyl, 1-(N,N-diethylcarbamoyl)ethyl, 2-(N,N-dimethylcarbamoyl)ethyl, 2-(N,N-diethylcarbamoyl)ethyl, 2-(N,N-dimethylcarbamoyl)prop-2-yl, 2-(N,N-diethylcarbamoyl)prop-2-yl, 3-(N,N-dimethylcarbamoyl)propyl or 3-(N,N-diethylcarbamoyl)propyl.

A suitable value for Ar¹ or Ar² when it is phenylene is, for example, 1,3- or 1,4-phenylene.

A suitable value for A¹ when it is (1-4C)alkylene is, for example, methylene, ethylene or trimethylene.

A suitable value for Ar² when it is pyridinediyl, pyrimidinediyl, thiophenediyl, furandiyl, thiazolediyl, oxazolediyl, thiadiazolediyl or oxadiazolediyl is, for example, 2,4- or 3,5-pyridinediyl, 4,6-pyrimidinediyl, 2,4- or 2,5-thiophenediyl, 2,4or 2,5-furandiyl, 2,4- or 2,5-thiadiazolediyl, 2,4- or 2,5-oxazolediyl, 2,5-thiadiazolediyl or 2,5-oxadiazolediyl.

A suitable value for R¹ when it is (1-4C)alkyl is, for example, methyl, ethyl, propyl or butyl; when it (3-4C)alkenyl is, for example allyl, 2-butenyl or 3-butenyl; and when it is (3-4C)alkynyl is, for example, 2-propynyl or 2-butynyl.

When R² and R³ together form a group of the formula --A² --X² --A³ -- which together with the carbon atom to which A² and A³ are attached define a ring having 5 or 6 ring atoms then a suitable value for A² or A³, which may be the same or different, when each is (1-3C)alkylene is, for example, methylene, ethylene or trimethylene. Suitable values for the substituents which may be present on said 5- or 6-membered ring include, for example:

    ______________________________________                                         for (1-4C) alkyl:                                                                            methyl, ethyl, propyl, isopropyl, butyl                                        and isobutyl;                                                    for (1-4C) alkoxy:                                                                           methoxy, ethoxy, propoxy, isopropoxy                                           and butoxy.                                                      ______________________________________                                    

Said substituents may be located on any available position including, when the substituent is (1-4C)alkyl, on the nitrogen atom when X² is imino.

When R¹ and R² together form a group of the formula --A² --X² --A³ -- which together with the oxygen atom to which A² is attached and with the carbon atom to which A³ is attached define a ring having 5 or 6 ring atoms then a suitable value for A² and A³, which may be the same or different, when each is (1-3C)alkylene is, for example, methylene, ethylene or trimethylene. Suitable values for the (1-4C)alkyl substituents which may be present on said 5- or 6-membered ring include, for example, methyl, ethyl, propyl, isopropyl and butyl.

A suitable value for R³ when it is (1-4C)alkyl is, for example, methyl, ethyl, propyl or butyl; when it is (2-4C)alkenyl is, for example, vinyl, allyl, 2-butenyl or 3-butenyl; and when it is (2-4C)alkynyl is, for example, ethynyl, 2-propynyl or 2-butynyl.

A suitable pharmaceutically-acceptable salt of a compound of the invention is, for example, an acid-addition salt of a compound of the invention which is sufficiently basic, for example, an acid-addition salt with, for example, an inorganic or organic acid, for example hydrochloric, hydrobromic, sulphuric, phosphoric, trifluoroacetic, citric or maleic acid. In addition a suitable pharmaceutically-acceptable salt of a compound of the invention which is sufficiently acidic is an alkali metal salt, for example a sodium or potassium salt, an alkaline earth metal salt, for example a calcium or magnesium salt, an ammonium salt or a salt with an organic base which affords a physiologically-acceptable cation, for example a salt with methylamine, dimethylamine, trimethylamine, piperidine, morpholine or tris-(2-hydroxyethyl)amine.

Particular compounds of the invention include, for example, hydroxylamine derivatives of the formula I, or pharmaceutically-acceptable salts thereof, wherein:

(a) R⁴ is hydrogen, carbamoyl, (2-5C)alkanoyl, benzoyl or phenylsulphonyl and wherein said benzoyl or phenylsulphonyl group may optionally bear one or two substituents selected from halogeno, (1-4C)alkyl and (1-4C)alkoxy; and R⁵, R⁶, R⁷, Ar¹, A¹, X¹, Ar², R¹, R² and R³ have any of the meanings defined hereinbefore or in this section defining particular compounds;

(b) R⁵ is hydrogen, (1-4C)alkyl, (2-5C)alkanoyl, halogeno-(2-4C)alkyl, cyano-(1-4C)alkyl, (1-4C)alkoxycarbonyl(1-4C)alkyl or phenyl-( 1-4C)alkyl and wherein said phenyl-(1-4C)alkyl group may optionally bear one or two substituents selected from halogeno, (1-4C)alkyl and (1-4C)alkoxy; and R⁴, R⁶, R⁷, Ar¹, A¹, X¹, Ar², R¹, R² and R³ have any of the meanings defined hereinbefore or in this section defining particular compounds;

(c) R⁶ is hydrogen, (1-4C)alkyl or phenyl and wherein said phenyl group may optionally bear one or two substituents selected from halogeno, (1-4C)alkyl and (1-4C)alkoxy; and R⁴, R⁵, R⁷, Ar¹, A¹, X¹, Ar², R¹, R² and R³ have any of the meanings defined hereinbefore or in this section defining particular compounds;

(d) R⁷ is hydrogen; and R⁴, R⁵, R⁶, Ar¹, A¹, X¹, Ar², R¹, R² and R³ have any of the meanings defined hereinbefore or in this section defining particular compounds;

(e) Ar¹ is phenylene which may optionally bear one or two substituents selected from halogeno, (1-4C)alkyl and (1-4C)alkoxy; and R⁴, R⁵, R⁶, R⁷, A¹, X¹, Ar², R¹, R² and R³ have any of the meanings defined hereinbefore or in this section defining particular compounds;

(f) Ar¹ is 1,4-phenylene and R⁶ is linked to Ar¹ ortho to the --C(R⁶)(R⁷)-- group and defines an ethylene or vinylene group, or a group of the formula

    --(CH.sub.2).sub.n --X.sup.3 --

wherein n is 2 and X³ is oxy; and R⁴, R⁵, R⁷, A¹, X¹, Ar², R¹, R² and R³ have any of the meanings defined hereinbefore or in this section defining particular compounds;

(g) A¹ is a direct link to X¹ ; and R⁴, R⁵, R⁶, R⁷, Ar¹, Ar², R¹, R² and R³ have any of the meanings defined hereinbefore or in this section defining particular compounds;

(h) A¹ is (1-4C)alkylene and X¹ is oxy; and R⁴, R⁵, R⁶, R⁷, Ar¹, Ar², R¹, R² and R³ have any of the meanings defined hereinbefore or in this section defining particular compounds;

(i) A¹ is a direct link to X¹ and X¹ is thio; and R⁴, R⁵, R⁶, R⁷, Ar¹, Ar², R¹, R² and R³ have any of the meanings defined hereinbefore or in this section defining particular compounds;

(j) Ar² is phenylene which may optionally bear one or two substituents selected from halogeno, trifluoromethyl, (1-4C)alkyl and (1-4C)alkoxy, or Ar² is pyridinediyl or thiophenediyl; and R⁴, R⁵, R⁶, R⁷, Ar¹, A¹, X¹, R¹, R² and R³ have any of the meanings defined hereinbefore or in this section defining particular compounds;

(k) R¹ is (1-4C)alkyl; and R⁴, R⁵, R⁶, R⁷, Ar¹, A¹, X¹, Ar², R² and R³ have any of the meanings defined hereinbefore or in this section defining particular compounds;

(l) R² and R³ together form a group of the formula --A² --X² --A³ -- which together with the carbon atom to which A² and A³ are attached define a ring having 5 or 6 ring atoms, wherein each of A² and A³ is independently (1-3C)alkylene and X² is oxy, and which ring may optionally bear one or two (1-4C)alkyl substituents; and R⁴, R⁵, R⁶, R⁷, Ar¹, A¹, X¹ Ar² and R¹ have any of the meanings defined hereinbefore or in this section defining particular compounds; or

(m) R¹ and R² together form a group of the formula --A² --X² --A³ -- which together with the oxygen atom to which A² is attached and with the carbon atom to which A³ is attached define a ring having 5 ring atoms, wherein each of A² and A³ is methylene and X² is oxy, and which ring may optionally bear one or two substituents selected from methyl and ethyl, and R³ is methyl or ethyl; and R⁴, R⁵, R⁶, R⁷, Ar¹, A¹, X¹ and Ar² have any of the meanings defined hereinbefore or in this section defining particular compounds.

A preferred compound of the invention comprises a hydroxylamine derivative of the formula I

wherein

R⁴ is hydrogen, carbamoyl, acetyl, propionyl, benzoyl or phenylsulphonyl and wherein said benzoyl or phenylsulphonyl group may optionally bear one substituent selected from fluoro, chloro, methyl and methoxy;

R⁵ is hydrogen, methyl, ethyl, propyl, acetyl, propionyl, 2-fluoroethyl, 2-chloroethyl, cyanomethyl, methoxycarbonylmethyl or ethoxycarbonylmethyl;

R⁶ is hydrogen, methyl, ethyl or phenyl and wherein said phenyl group may optionally bear one substituent selected from fluoro, chloro, methyl and methoxy;

R⁷ is hydrogen;

Ar¹ is 1,4-phenylene which may optionally bear one substituent selected from fluoro, chloro, methyl and methoxy;

A¹ is a direct link to X¹ and X¹ is thio, or A¹ is methylene and X¹ is oxy;

Ar² is 1,3- or 1,4-phenylene which may optionally bear one or two substituents selected from fluoro, chloro, trifluoromethyl, methyl and methoxy, or Ar² is 3,5-pyridinediyl, 2,4-thiophenediyl or 2,5-thiophenediyl;

R¹ is methyl, ethyl or allyl; and

R² and R³ together form a group of the formula --A² --X² --A³ -- which together with the carbon atoms to which A² and A³ are attached define a ring having 6 ring atoms, wherein each of A² and A³ is ethylene and X² is oxy, and which ring may optionally bear one or two substituents selected from methyl and ethyl;

or a pharmaceutically-acceptable salt thereof.

A further preferred compound of the invention comprises a hydroxylamine derivative of the formula I

wherein

R⁴ is hydrogen, carbamoyl, acetyl, benzoyl or phenylsulphonyl;

R⁵ is hydrogen, methyl, ethyl, acetyl, 2-fluoroethyl or cyanomethyl;

R⁶ is hydrogen, methyl or ethyl;

R⁷ is hydrogen;

Ar¹ is 1,4-phenylene;

A¹ is a direct link to X¹ ;

X¹ is thio;

Ar² is 1,3-phenylene which may optionally bear one or two substituents selected from fluoro and chloro, or Ar² is 2,4- or 2,5-thiophenediyl;

R¹ is methyl, ethyl or allyl; and

R² and R³ together form a group of the formula --A² --X² --A³ -- which together with the carbon atom to which A² and A³ are attached define a ring having 6 ring atoms, wherein each of A² and A³ is ethylene and X² is oxy, and which ring may optionally bear one or two methyl substituents;

or a pharmaceutically-acceptable salt thereof.

A further preferred compound of the invention comprises a hydroxylamine derivative of the formula I

wherein

R⁴ is hydrogen, carbamoyl, acetyl or phenylsulphonyl;

R⁵ is hydrogen or methyl;

R⁶ is methyl;

R⁷ is hydrogen;

Ar¹ is 1,4-phenylene;

A¹ is a direct link to X¹ ;

X¹ is thio;

Ar² is 1,3-phenylene, 5-fluoro-1,3-phenylene or 2,4-thiophenediyl (with the X¹ group in the 2-position);

R¹ is methyl; and

R² and R³ together form a group of the formula --A² --X² --A³ -- which together with the carbon atom to which A² and A³ are attached define a ring having 6 ring atoms, wherein each of A² and A³ is ethylene and X² is oxy, and which ring may optionally bear a methyl substituent alpha to X² ;

or a pharmaceutically-acceptable salt thereof.

A specific especially preferred compound of the invention is, for example, the following hydroxylamine derivative of the formula I, or a pharmaceutically-acceptable salt thereof:

N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-α-methylbenzyl}-O-methylhydroxylamine,

O-acetyl-N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-.alpha.-methylbenzyl}acetohydroxamic acid or

N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-α-methylbenzyl}-N-hydroxyurea.

A compound of the invention comprising a hydroxylamine derivative of the formula I, or a pharmaceutically-acceptable salt thereof, may be prepared by any process known to be applicable to the preparation of structurally-related compounds. Such procedures are provided as a further feature of the invention and are illustrated by the following representative examples in which, unless otherwise stated, R⁴, R⁵, R⁶, R⁷, Ar¹, A¹, X¹, Ar², R¹, R² and R³ have any of the meanings defined hereinbefore, provided that when there is an amino, alkylamino, carboxy or hydroxy group in R⁵ or an imino group in the ring defined by R² and R³ then any such group may optionally be protected by a conventional protecting group which may be removed when so desired by conventional means.

(a) For those compounds of the invention wherein each of R⁴ and R⁷ is hydrogen, the reduction of an oxime of the formula II ##STR3##

Any reducing agent known in the art for the reduction of an oxime to a hydroxylamine may be employed. A suitable reducing agent is, for example, a hydride reducing agent, for example an alkali metal aluminium hydride such as lithium aluminium hydride or a borane-based hydride such as diborane, borane-pyridine complex, borane-trimethylamine complex, borane-tetrahydrofuran complex or borane-dimethyl sulphide complex.

The reduction is conveniently performed in a suitable inert solvent or diluent, for example, 1,2-dimethoxyethane or tetrahydrofuran. A less powerful reducing agent such as borane-pyridine complex may be used in a protic solvent, for example, a (1-4C)alcohol such as methanol, ethanol and propanol. The reaction is conveniently performed at a temperature in the range, for example, -10° to 100° C., conveniently at or near 0° C.

The starting materials of the formula II may be obtained by standard procedures of organic chemistry. The preparation of such starting materials is described within the accompanying non-limiting Examples. Thus, for example, the starting material of the formula II may be obtained by the reaction of a compound of the formula III ##STR4## with a hydroxylamine of the formula R⁵ O--NH₂.

The reaction is conveniently performed in a suitable inert solvent or diluent, for example, one or more of water, a (1-4C)alcohol such as methanol, ethanol and propanol, pyridine, 1,2-dimethoxyethane, tetrahydrofuran or a dipolar aprotic solvent such as N,N-dimethylformamide and dimethylsulphoxide. The reaction is conveniently performed at a temperature in the range, for example, 10° to 150° C., conveniently at or near 70° C.

The starting materials of the formula III may be obtained by standard procedures of organic chemistry. The preparation of such starting materials is described within the accompanying non-limiting Examples. Alternatively necessary starting materials are obtainable by analogous procedures to those illustrated which are within the ordinary skill of an organic chemist. The disclosures of European Patent Applications Nos. 00375404, 0385662, 0409413 and 0420511 are particularly relevant to the preparation of suitable starting materials.

Alternatively, for the production of those starting materials of the formula II wherein R⁵ is (1-4C)alkyl or substituted-alkyl, the alkylation, conveniently in the presence of a suitable base, of an oxime of the formula IV ##STR5## (itself obtainable by the reaction of the compound of the formula III with hydroxylamine) with an alkylating agent of the formula R⁵ --Z, wherein Z is a displaceable group.

A suitable displaceable group Z is, for example, a halogeno or sulphonyloxy group, for example a chloro, bromo, iodo, methanesulphonyloxy or toluene-4-sulphonyloxy group.

A suitable base for the reaction is, for example, an alkali or alkaline earth metal carbonate, (1-4C)alkoxide, hydroxide or hydride, for example sodium carbonate, potassium carbonate, sodium ethoxide, potassium butoxide, sodium hydroxide, potassium hydroxide, sodium hydride or potassium hydride. The reaction is conveniently performed in a suitable inert solvent or diluent, for example N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulphoxide, acetone, 1,2-dimethoxyethane or tetrahydrofuran, and at a temperature in the range, for example, 10° to 150° C., conveniently at or near ambient temperature.

(b) For the production of those compounds of the formula I wherein R⁴ is (2-5C)alkanoyl or optionally-substituted phenylsulphonyl, the reaction, conveniently in the presence of a suitable base as defined hereinbefore, of a hydroxylamine of the formula V ##STR6## with a (2-5C)alkanoyl halide such as a (2-5C)alkanoyl chloride or bromide, with a (2-5C)alkanoic acid anhydride or with an optionally-substituted phenylsulphonyl halide such as a phenylsulphonyl chloride or bromide.

A suitable base for the reaction is, for example, an alkali or alkaline earth metal carbonate, (1-4C)alkoxide, hydroxide or hydride, for example sodium carbonate, potassium carbonate, sodium ethoxide, potassium butoxide, sodium hydroxide, potassium hydroxide, sodium hydride or potassium hydride. The reaction is conveniently performed in a suitable inert solvent or diluent, for example in a (1-4C)alcohol such as methanol, ethanol, propanol and isopropanol, in a dipolar aprotic solvent such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulphoxide and acetone, in 1,2-dimethoxyethane or in tetrahydrofuran, and at a temperature in the range, for example, 10° to 150° C., conveniently at or near ambient temperature.

It will be appreciated that when R⁵ is hydrogen, the above-mentioned reactions may result in acylation or sulphonylation of one or both of the oxygen and nitrogen heteroatoms of the hydroxylamine group. When it is desired to obtain only the O-acylated or O-sulphonylated derivative, the O,N-diacylated or O,N-disulphonylated derivative may be hydrolsed by conventional means, for example by hydrolysis with a base such as an alkali metal or alkaline earth metal (1-4C)alkoxide or hydroxide such as sodium ethoxide, potassium butoxide, sodium hydroxide, potassium hydroxide or lithium hydroxide.

(c) For the production of those compounds of the formula I wherein R⁴ is carbamoyl or N-(1-4C)alkylcarbamoyl, the reaction of a hydroxylamine of the formula V with an isocyanate of the formula R'--N═C═O, wherein R' is an alkali metal cyanate such as sodium or potassium cyanate, a tri-(1-4C)alkylsilylisocyanate such as trimethylisocyanate or a (1-4C)alkylisocyanate.

The reaction is conveniently performed in a suitable inert solvent or diluent such as 1,2-dimethoxyethane, tetrahydrofuran or 1,4-dioxane, and at a temperature in the range, for example, 25° to 150° C., conveniently at or near 100° C.

It will be appreciated that when a tri-(1-4C)alkylsilylisocyanate is used the N-tri-(1-4C)alkylsilylurea initially obtained is hydrolysed in a conventional aqueous work-up to afford the corresponding N--H urea.

(d) The alkylation, conveniently in the presence of a suitable base as defined hereinbefore, of a hydroxylamine of the formula R⁵ O--NH₂ with an alkylating agent of the formula VI ##STR7## wherein Z is a displaceable group as defined hereinbefore.

The reaction is conveniently performed in a suitable inert solvent or diluent such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulphoxide, acetone 1,2-dimethoxyethane, tetrahydrofuran and 1,4-dioxane, and at a temperature in the range, for example, 25° to 150° C., conveniently at or near 100° C.

The starting materials of the formula VI may be obtained by standard procedures of organic chemistry which are within the ordinary skill of an organic chemist, for example (when Z is bromo) by the bromination of the corresponding benzyl alcohol by conventional means.

Conventional protecting groups for an amino, alkylamino, carboxy or hydroxy group which may be present in R⁵ or an imino group in the ring defined by R² and R³ are set out hereinafter.

A suitable protecting group for an amino, imino or alkylamino group is, for example, an acyl group for example a (2-4C)alkanoyl group (especially acetyl), a (1-4C)alkoxycarbonyl group (especially methoxycarbonyl, ethoxycarbonyl or tert-butoxycarbonyl), an arylmethoxycarbonyl group (especially benzyloxycarbonyl) or an aroyl group (especially benzoyl). The deprotection conditions for the above protecting groups necessarily vary with the choice of protecting group. Thus, for example, an acyl group such as an alkanoyl or alkoxycarbonyl or an aroyl group may be removed for example, by hydrolysis with a suitable base such as an alkali metal hydroxide, for example lithium or sodium hydroxide. Alternatively an acyl group such as a tert-butoxycarbonyl group may be removed, for example, by treatment with a suitable acid such as hydrochloric, sulphuric or phosphoric acid or trifluoroacetic acid and an arylmethoxycarbonyl group such as a benzyloxycarbonyl group may be removed, for example, by hydrogenation over a catalyst such as palladium-on-charcoal.

A suitable protecting group for a carboxy group is, for example, an esterifying group, for example a (1-4C)alkyl group (especially methyl or ethyl) which may be removed, for example, by hydrolysis with a suitable base such as an alkali metal hydroxide, for example lithium or sodium hydroxide; or, for example, a tert-butyl group which may be removed, for example, by treatment with a suitable acid such as hydrochloric, sulphuric or phosphoric acid or trifluoroacetic acid.

A suitable protecting group for a hydroxy group is, for example, an acyl group, for example a (2-4C)alkanoyl group (especially acetyl), an aroyl group (especially benzoyl) or an arylmethyl group (especially benzyl). The deprotection conditions for the above protecting groups will necessarily vary with the choice of protecting group. Thus, for example, an acyl group such as an alkanoyl or an aroyl group may be removed, for example, by hydrolysis with a suitable base such as an alkali metal hydroxide, for example lithium or sodium hydroxide. Alternatively an arylmethyl group such as a benzyl group may be removed, for example, by hydrogenation over a catalyst such as palladium-on-charcoal.

When a pharmaceutically-acceptable salt of a compound of the formula I is required, it may be obtained, for example, by reaction of said compound with a suitable acid or base using a conventional procedure. When an optically active form of a compound of the formula I is required, it may be obtained by carrying out one of the aforesaid procedures using an optically active starting material, or by resolution of a racemic form of said compound using a conventional procedure.

As stated previously, the compounds of the formula I are inhibitors of the enzyme 5-LO. The effects of this inhibition may be demonstrated using one or more of the standard procedures set out below:

a) An in vitro assay system involving incubating a test compound with heparinised human blood, prior to challenge with the calcium ionophore A²³¹⁸⁷ and then indirectly measuring the inhibitory effects on 5-LO by assaying the amount of LTB₄ using specific radioimmunoassays described by Carey and Forder (Prostaglandins, Leukotrienes Med., 1986, 22, 57; Prostaglandins, 1984, 28, 666; Brit. J. Pharmacol., 1985, 84, 34P) which involves the use of a protein-LTB₄ conjugate produced using the procedure of Young et alia (Prostaglandins, 1983, 26(4), 605-613). The effects of a test compound on the enzyme cyclooxygenase (which is involved in the alternative metabolic pathway for arachidonic acid and gives rise to prostaglandins, thromboxanes and related metabolites) may be measured at the same time using the specific radioimmunoassay for thromboxane B₂ (TxB₂) described by Carey and Forder (see above). This test provides an indication of the effects of a test compound against 5-LO and also cyclooxygenase in the presence of blood cells and proteins. It permits the selectivity of the inhibitory effect on 5-LO or cyclooxygenase to be assessed.

b) An ex vivo assay system, which is a variation of test a) above, involving administration to a group of rats of a test compound (usually orally as the suspension produced when a solution of the test compound in dimethylsulphoxide is added to carboxymethylcellulose), blood collection, heparinisation, challenge with A23187 and radioimmunoassay of LTB₄ and TxB₂. This test provides an indication of the bioavailability of a test compound as an inhibitor of 5-LO or cyclooxygenase.

c) An in vivo system involving measuring the effects of a test compound administered orally against the liberation of LTB₄ induced by zymosan within an air pouch generated within the subcutaneous tissue of the back of male rats. The rats are anaesthetised and air pouches are formed by the injection of sterile air (20 ml). A further injection of air (10 ml) is similarly given after 3 days. At 6 days after the initial air injection the test compound is administered (usually orally as the suspension produced when a solution of the test compound in dimethylsulphoxide is added to hydroxypropylmethylcellulose), followed by the intrapouch injection of zymosan (1 ml of a 1% suspension in physiological saline). After 3 hours the rats are killed, the air pouches are lavaged with physiological saline, and the specific radioimmunoassay described above is used to assay LTB₄ in the washings. This test provides an indication of inhibitory effects against 5-LO in an inflammatory milieu.

Although the pharmacological properties of the compounds of the formula I vary with structural changes as expected, in general compounds of the formula I possess 5-LO inhibitory effects at the following concentrations or doses in one or more of the above tests a)-c):

Test a):

IC₅₀ (LTB₄) in the range, for example, 0.01-40 μM

IC₅₀ (TxB2) in the range, for example, 40-200 μM;

Test b):

oral ED₅₀ (LTB₄) in the range, for example, 0.1-100 mg/kg;

Test c):

oral ED₅₀ (LTB4) in the range, for example, 0.1-50 mg/kg.

No overt toxicity or other untoward effects are present in tests b) and/or c) when compounds of the formula I are administered at several multiples of their minimum inhibitory dose or concentration.

Thus, by way of example, the compound N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-α-methylbenzyl}-O-methylhydroxylamine has an IC₅₀ of 0.04 μM against LTB₄ in test a) and an oral ED₅₀ of approximately 0.5 mg/kg versus LTB₄ in test c); the compound O-acetyl-N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-.alpha.-methylbenzyl}acetohydroxamic acid has an IC₅₀ of 0.15 μM against LTB₄ in test a) and an oral ED₅₀ of approximately 0.5 mg/kg versus LTB₄ in test c); and the compound N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-α-methylbenzyl}-N-hydroxyurea has an IC₅₀ of 0.57 μM against LTB₄ in test a) and an oral ED₅₀ of approximately 0.5mg/kg versus LTB₄ in test c).

In general those compounds of the formula I which are particularly preferred have an IC₅₀ of <1 μM against LTB₄ in test a) and an oral ED₅₀ of <100 mg/kg against LTB₄ in tests b) and/or c).

These compounds are examples of compounds of the invention which show selective inhibitory properties for 5-LO as opposed to cyclooxygenase, which selective properties are expected to impart improved therapeutic properties, for example, a reduction in or freedom from the gastrointestinal side-effects frequently associated with cyclooxygenase inhibitors such as indomethacin.

According to a further feature of the invention there is provided a pharmaceutical composition which comprises a hydroxylamine derivative of the formula I, or a pharmaceutically-acceptable salt thereof, in association with a pharmaceutically-acceptable diluent or carrier.

The composition may be in a form suitable for oral use, for example a tablet, capsule, aqueous or oily solution, suspension or emulsion; for topical use, for example a cream, ointment, gel or aqueous or oily solution or suspension; for nasal use, for example a snuff, nasal spray or nasal drops; for vaginal or rectal use, for example a suppository; for administration by inhalation, for example as a finely divided powder such as a dry powder, a microcrystalline form or a liquid aerosol; for sub-lingual or buccal use, for example a tablet or capsule; or for parenteral use (including intravenous, subcutaneous, intramuscular, intravascular or infusion), for example a sterile aqueous or oily solution or suspension. In general the above compositions may be prepared in a conventional manner using conventional excipients.

The amount of active ingredient (that is a hydroxylamine derivative of the formula I, or a pharmaceutically-acceptable salt thereof) that is combined with one or more excipients to produce a single dosage form will necessarily vary depending upon the host treated and the particular route of administration. For example, a formulation intended for oral administration to humans will generally contain, for example, from 0.5 mg to 2 g of active agent compounded with an appropriate and convenient amount of excipients which may vary about 5 to about 98 percent by weight of the total composition. Dosage unit forms will generally contain about 1 mg to about 500 mg of an active ingredient.

According to a further feature of the invention there is provided a hydroxylamine derivative of the formula I, or a pharmaceutically-acceptable salt thereof, for use in a method of treatment of the human or animal body by therapy.

The invention also includes a method of treating a disease or medical condition mediated alone or in part by one or more leukotrienes which comprises administering to a warm-blooded animal requiring such treatment an effective amount of an active ingredient as defined above. The invention also provides the use of such an active ingredient in the production of a new medicament for use in a leukotriene mediated disease or medical condition.

The size of the dose for therapeutic or prophylactic purposes of a compound of the formula I will naturally vary according to the nature and severity of the conditions, the age and sex of the animal or patient and the route of administration, according to well known principles of medicine. As mentioned above, compounds of the formula I are useful in treating those allergic and inflammatory conditions which are due alone or in part to the effects of the metabolites of arachidonic acid arising by the linear (5-LO catalysed) pathway and in particular the leukotrienes, the production of which is mediated by 5-LO. As previously mentioned, such conditions include, for example, asthmatic conditions, allergic reactions, allergic rhinitis, allergic shock, psoriasis, atopic dermatitis, cardiovascular and cerebrovascular disorders of an inflammatory nature, arthritic and inflammatory joint disease, and inflammatory bowel diseases.

In using a compound of the formula I for therapeutic or prophylactic purposes it will generally be administered so that a daily dose in the range, for example, 0.5 mg to 75 mg per kg body weight is received, given if required in divided doses. In general lower doses will be administered when a parenteral route is employed. Thus, for example, for intravenous administration, a dose in the range, for example, 0.5 mg to 30 mg per kg body weight will generally be used. Similarly, for administration by inhalation, a dose in the range, for example, 0.5 mg to 25 mg per kg body weight will be used.

Although the compounds of the formula I are primarily of value as therapeutic agents for use in warm-blooded animals (including man), they are also useful whenever it is required to inhibit the enzyme 5-LO. Thus, they are useful as pharmacological standards for use in the development of new biological tests and in the search for new pharmacological agents.

By virtue of their effects on leukotriene production, the compounds of the formula I have certain cytoprotective effects, for example they are useful in reducing or suppressing certain of the adverse gastrointestinal effects of the cyclooxygenase inhibitory non-steroidal anti-inflammatory agents (NSAIA), such as indomethacin, acetylsalicylic acid, ibuprofen, sulindac, tolmetin and piroxicam. Furthermore, co-administration of a 5-LO inhibitor of the formula I with a NSAIA can result in a reduction in the quantity of the latter agent needed to produce a therapeutic effect, thereby reducing the likelihood of adverse side-effects. According to a further feature of the invention there is provided a pharmaceutical composition which comprises a hydroxylamine derivative of the formula I, or a pharmaceutically-acceptable salt thereof as defined hereinbefore, in conjunction or admixture with a cyclooxygenase inhibitory non-steroidal anti-inflammatory agent (such as those mentioned above), and a pharmaceutically-acceptable diluent or carrier.

The cytoprotective effects of the compounds of the formula I may be demonstrated, for example in a standard laboratory model which assesses protection against indomethacin-induced or ethanol-induced ulceration in the gastrointestinal tract of rats.

The compositions of the invention may in addition contain one or more therapeutic or prophylactic agents known to be of value for the disease under treatment. Thus, for example a known platelet aggregation inhibitor, hypolipidemic agent, anti-hypertensive agent, beta-adrenergic blocker or a vasodilator may usefully also be present in a pharmaceutical composition of the invention for use in treating a heart or vascular disease or condition. Similarly, by way of example, an anti-histamine, steroid (such as beclomethasone dipropionate), sodium cromoglycate, phosphodiesterase inhibitor or a beta-adrenergic stimulant may usefully also be present in a pharmaceutical composition of the invention for use in treating a pulmonary disease or condition.

The invention will now be illustrated in the following non-limiting Examples in which, unless otherwise stated:

(i) evaporations were carried out by rotary evaporation in vacuo and work-up procedures were carried out after removal of residual solids by filtration;

(ii) operations were carried out at ambient temperature, that is in the range 18°-25° C. and under an atmosphere of an inert gas such as argon;

(iii) column chromatography (by the flash procedure) and medium pressure liquid chromatography (MPLC) were performed on Merck Kieselgel silica (Art. 9385) or Merck Lichroprep RP-18 (Art. 9303) reversed-phase silica obtained from E. Merck, Darmstadt, W. Germany;

(iv) yields are given for illustration only and are not necessarily the maximum attainable;

(v) the structures of the end-products of the formula I were confirmed by NMR and mass spectral techniques; unless otherwise stated, CDCl₃ solutions of the end-products of the formula I were used for the determination of the NMR spectral data, chemical shift values were measured on the delta scale and the following abbreviations are used: s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet;

(vi) intermediates were not generally fully characterised and purity was assessed by thin layer chromatographic, infra-red (IR) or NMR analysis;

(vii) melting points are uncorrected and were determined using a Mettler SP62 automatic melting point apparatus or an oil-bath apparatus; melting points for the end-products of the formula I were determined after recrystallisation from a conventional organic solvent such as ethanol, methanol, acetone, ether or hexane, alone or in admixture;

(vii) the following abbreviations have been used:

    ______________________________________                                         THF             tetrahydrofuran;                                               DMF             N,N-dimethylformamide                                          DMSO            dimethylsulphoxide                                             ______________________________________                                    

EXAMPLE 1

Borane-pyridine complex (0.487 ml) was added dropwise to a stirred suspension of (E)-4'-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]acetophenone oxime (0.905 g) in ethanol (5 ml) which had been cooled to 0° C. The mixture was stirred at 0° C. for 10 minutes. A 20% w/v solution of hydrogen chloride in ethanol (4 ml) was added and the mixture was stirred at ambient temperature for 1 hour. Water (10 ml was added and the mixture was basified to pH9 by the addition of 2N aqueous sodium hydroxide. The mixture was extracted with ethyl acetate. The organic phase was washed with brine, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using a 2:1 v/v mixture of petroleum ether (b.p. 40°-60° C.) and ethyl acetate as eluent. There was thus obtained N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-α-methylbenzyl}hydroxylamine as an oil (0.379 g, 41 %);

NMR Spectrum: 1.41 (d, 3H), 1.8-2.05 (m, 4H), 2.97 (s, 3H), 3.7-3.9 (m, 4H), 4.15 (m, 1H), 6.7-7.5 (m, 7H); Elemental Analysis: Found C, 62.4; H, 6.5; N, 3.5; C₂₀ H₂₄ FNO₃ S. 0.4EtAc requires C, 62.9; H, 6.6; N, 3.4%.

The (E)-4'-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl )phenylthio]acetophenone oxime used as a starting material was obtained as follows:

A mixture of 4'-iodoacetophenone (2.46 g), 4-(5-fluoro-3-mercaptophenyl)-4-methoxytetrahydropyran (European Patent Application No. 0420511, Example 4 thereof; 1.61 g), potassium carbonate (2.76 g), cuprous chloride (0.4 g) and DMF (10 ml) was stirred and heated to 140° C. for 2 hours. The mixture was cooled to ambient temperature and partitioned between diethyl ether and water. The organic phase was washed with brine, dried (MgSO₄) and evaporated. The product was purified by column chromatography using initially methylene chloride and then increasingly polar mixtures of methylene chloride and diethyl ether as eluent. There was thus obtained 4'-[5-fluoro-3-(4 -methoxytetrahydropyran-4-yl)phenylthio]acetophenone (1.62 g, 45%) m.p. 86°-87° C.

After repetition of the above reaction, a mixture of the product so obtained (2.6 g), hydroxylamine hydrochloride (0.6 g), barium carbonate (1.7 g), water (15 ml) and ethanol (75 ml) was stirred and heated to reflux for 5 hours. The bulk of the ethanol was evaporated and the residue was partitioned between diethyl ether and water. The organic phase was washed with brine, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using a 10:1 v/v mixture of methylene chloride and diethyl ether as eluent. There was thus obtained the required starting material (2.3 g, 85%), m.p. 155°-156° C;

NMR Spectrum: 1.8-2.1 (m, 4H), 2.27 (s, 3H), 2.98 (s, 3H), 3.7-3.9 (m, 4H), 6.8-7.7 (m, 7H).

EXAMPLE 2

Using an analogous procedure to that described in Example 1, (E)-4'-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]acetophenone oxime O-methyl ether was reduced to give N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-α-methylbenzyl}-O-methylhydroxylamine in 81% yield as an oil;

NMR Spectrum: 1.3 (d, 3H), 1.7-2.0 (m, 4H), 2.9 {s, 3H), 3.3 (s, 3H), 3.6-3.8 (m, 4H), 4.1 (q, 1H), 6.6-7.4 (m, 7H); Elemental Analysis: Found C, 63.9; H, 6.5; N, 3.5; C₂₁ H₂₆ FNO₃ S requires C, 64.4; H, 6.7; N, 3.6%.

The (E)-4'-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]acetophenone oxime O-methyl ether used as a starting material was obtained as follows:

Sodium hydride (60% w/w dispersion in mineral oil, 0.024 g) was added to a stirred solution of (E)-4'-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]acetophenone oxime (0.14 g) in THF (5 ml) and the mixture was stirred at ambient temperature for 10 minutes. Methyl iodide (0.212 g) was added and the mixture was stirred at ambient temperature for 16 hours. The mixture was partitioned between diethyl ether and water. The organic phase was washed with brine, dried (MgSO₄) and evaporated. The product was purified by column chromatography using increasingly polar mixtures of methylene chloride and diethyl ether as eluent. There was thus obtained the required starting material (0.075 g, 52%), m.p. 41°-42° C.;

NMR Spectrum: 1.8-2.0 (m, 4H), 2.20 (s, 3H), 2.97 (s, 3H), 3.7-3.9 (m, 4H), 3.98 (s, 3H), 6.75-7.70 (m, 7H).

EXAMPLE 3

Acetyl chloride (0.25 ml) was added dropwise to a stirred mixture of N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-α-methylbenzyl}hydroxylamine (0.44 g), pyridine (0.276 ml) and THF (10 ml) which had been cooled to 0° C. The mixture was stirred at ambient temperature for 1 hour. The mixture was partitioned between diethyl ether and dilute aqueous hydrochloric acid. The organic phase was washed with brine, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using a 10:1 v/v mixture of petroleum ether (b.p. 40°-60° C.) and ethyl acetate as eluent. There was thus obtained O-acetyl-N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-.alpha.-methylbenzyl}acetohydroxamic acid (0.34 g).

A mixture of the product so obtained, lithium hydroxide monohydrate (0.047 g) isopropanol (3 ml) and water (3 ml) was stirred at ambient temperature for 2 hours. The mixture was neutralised by the addition of 2N aqueous hydrochloric acid and extracted with diethyl ether. The organic extract was washed with brine, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using increasingly polar mixtures of petroleum ether (b.p. 40°-60° C.) and ethyl acetate as eluent. There was thus obtained N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-Yl)phenylthio]-α-methylbenzyl}acetohydroxamic acid as an oil (0.13 g, 41%);

NMR Spectrum: 1.65 (d, 3H), 1.75-2.0 (m, 4H), 2.16 (s, 3H), 2.98 (s, 3H), 3.65-3.8 (m, 4H), 5.4 (hump, 1H), 6.7-7.4 (m, 7H); Elemental Analysis: Found C, 62.6; H, 6.6; N, 3.0; C₂₂ H₂₆ FNO₄ S. 0.5CH₃ COCH₃ requires C, 62.9; H, 6.5; N, 3.1%.

EXAMPLE 4

Acetyl chloride (0.041 ml) was added to a stirred mixture of N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-α-methylbenzyl}-O-methylhydroxylamine (0.15 g), pyridine (0.047 ml) and THF (4 ml) which had been cooled to 0° C. The mixture was stirred at ambient temperature for 1 hour. The mixture was partitioned between diethyl ether and dilute aqueous hydrochloric acid. The organic phase was washed with brine, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using a 2:1 v/v mixture of petroleum ether (b.p. 40°-60° C.) and ethyl acetate as eluent. There was thus obtained N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-α-methylbenzyl}-O-methylhydroxamic acid as an oil (0.14 g, 85%);

NMR Spectrum: 1.62 (d, 3H), 1.8-2.1 (m, 4H), 2.15 (s, 3H), 2.97 (s, 3H), 3.52 (s, 3H), 3.7-3.9 (m, 4H), 5.7 (q, 1H), 6.75-7.5 (m, 7H); Elemental Analysis: Found C, 63.3; H, 6.8; N, 3.1; C₂₃ H₂₈ FNO₄ S requires C, 63.7; H, 6.5; N, 3.2%.

EXAMPLE 5

Benzenesulphonyl chloride (0.124 g) was added to a mixture of N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-α-methylbenzyl}-O-methylhydroxylamine (0.183 g), pyridine (0.057 ml) and THF (4 ml). The mixture was heated to 50° C. for 2 hours and then stirred at ambient temperature for 2 days. The mixture was evaporated and the residue was purified by column chromatography using a 5:1 v/v mixture of petroleum ether (b.p. 40°-60° C.) and ethyl acetate as eluent. There was thus obtained N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-α-methylbenzyl}-O-methylbenzenesulphonohydroxamic acid as a glass (0.07 g, 40%);

NMR Spectrum: 1.42 (d, 3H), 1.7-2.0 (m, 4H), 2.98 (s, 3H), 3.70 (s, 3H), 3.8-4.0 (m, 4H), 4.85 (q, 1H), 6.7-7.9 (m, 12H); Elemental Analysis: Found C, 60.9; H, 5.5; N, 2.6; C₂₇ H₃₀ FNO₅ S₂ requires C, 61.0; H, 5.7; N, 2.6%.

EXAMPLE 6

Trimethylsilylisocyanate (0.119 g) was added to a mixture of N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-α-methylbenzyl}hydroxylamine (0.277 g) and 1,4-dioxane (7 ml). The mixture was stirred and heated to reflux for 1 hour. The mixture was cooled to ambient temperature and partitioned between ethyl acetate and a saturated aqeuous ammonium chloride solution. The organic phase was washed with brine, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using initially a 5:2 v/v mixture of methylene chloride and acetone and then ethyl acetate as eluent. There was thus obtained N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-α-methylbenzyl)-N-hydroxyurea as a foam (0.04 g, 13%);

NMR Spectrum: 1.53 (d, 3H), 1.75-2.0 (m, 4H), 2.97 (s, 3H), 3.65-3.9 (m, 4H), 5.2 (broad s, 2H), 5.50 (q, 1H), 6.1 (broad s, 1H), 6.75-7.4 (m, 7H); Elemental Analysis: Found C, 59.8; H, 6.1; N, 6.4; C₂₁ H₂₅ FN₂ O₄ S requires C, 60.0; H, 6.0; N, 6.7%.

EXAMPLE 7

A mixture of 4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]benzyl chloride (0.366 g), N-methylhydroxylamine hydrochloride (0.167 g), potassium carbonate (0.52 g) and DMF (2 ml) was stirred and heated to 80° C. for 1 hour. The mixture was cooled to ambient temperature and partitioned between diethyl ether and water. The organic phase was washed with brine, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using increasingly polar mixtures of hexane and ethyl acetate as eluent. There was thus obtained N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]benzyl}-N-methylhydroxylamine (0.15 g, 40%), m.p. 100°-101° C. (recrystallised from a mixture of hexane and ethyl acetate); NMR Spectrum: 1.8-2.05 (m, 4H), 2.70 (s, 3H), 2.98 (s, 3H), 3.75-3.95 (m, 6H), 6.82 (m, 1H), 6.95 (m, 1H), 7.09 (m, 1H), 7.37 (m, 4H).

The 4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]benzyl chloride used as a starting material was obtained as follows:

A mixture of 4-(5-fluoro-3-mercaptophenyl)-4-methoxytetrahydropyran (European Patent Application No. 0420511, Example 4 thereof; 2.42 g), potassium hydroxide (0.56 g) and DMF (25 ml) was stirred and heated to 140° C. until a clear solution was obtained. 4-Bromobenzaldehyde (2.78 g) and cuprous oxide (0.715 g) were added and the mixture was stirred and heated to 140° C. for 90 minutes. The mixture was cooled to ambient temperature and partitioned between diethyl ether and water. The organic phase was washed with brine, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using a 4:1 mixture of petroleum ether (b.p. 40°-60° C.) and ethyl acetate as eluent. There was thus obtained 4-[5-fluoro-3-(4-methoxytetrahydropyran-4-Yl)phenylthio]benzaldehyde (2.38 g, 68%), m.p. 93° C.

Sodium borohydride (0.1 g) was added to a stirred mixture of a portion (0.87 g) of the benzaldehyde so obtained and ethanol (20 ml). The mixture was stirred at ambient temperature for 30 minutes. Acetic acid (1 ml) and water (50 ml) were added and the mixture was extracted with diethyl ether. The organic phase was washed with brine, dried (Na₂ SO₄) and evaporated. The residue was purified by column chromatography using increasingly polar mixtures of hexane and ethyl acetate as eluent. There was thus obtained 4-[5-fluoro-3-(4hydroxymethylphenylthio)phenyl]-4-methoxytetrahydropyran as a gum (0.85 g, 97%).

NMR Spectrum: 1.91 (m, 4H), 2.98 (s, 3H), 3.80 (m, 4H), 4.72 (s, 2H), 6.79 (m, 1H), 6.92 (m, 1H), 7.10 (m, 1H), 7.39 (m, 4H).

Thionyl chloride (0.1 ml) was added to a stirred mixture of a portion (0.348 g) of the material so obtained, pyridine (0.2 ml) and methylene chloride (5 ml) and the mixture was stirred at ambient temperature for 1 hour. The mixture was evaporated, toluene (5 ml) was added and the mixture was evaporated. There was thus obtained the required starting material as a gum (0.366 g) which was used without further purification.

EXAMPLE 8

The following illustrate representative pharmaceutical dosage forms containing the compound of formula I, or a pharmaceutically-acceptable salt thereof (hereafter compound X), for therapeutic or prophylactic use in humans:

    ______________________________________                                                                    mg/tablet                                           (a) Tablet I                                                                       Compound X             100                                                     Lactose Ph.Eur         182.75                                                  Croscarmellose sodium  12.0                                                    Maize starch paste (5% w/v paste)                                                                     2.25                                                    Magnesium stearate     3.0                                                 (b) Tablet II                                                                      Compound X             50                                                      Lactose Ph.Eur         223.75                                                  Croscarmellose sodium  6.0                                                     Maize starch           15.0                                                    Polyvinylpyrrolidone (5% w/v paste)                                                                   2.25                                                    Magnesium stearate     3.0                                                 (c) Tablet III                                                                     Compound X             1.0                                                     Lactose Ph.Eur         93.25                                                   Croscarmellose sodium  4.0                                                     Maize starch paste (5% w/v paste)                                                                     0.75                                                    Magnesium stearate     1.0                                                 (d) Capsule                mg/capsule                                              Compound X             10                                                      Lactose Ph. Eur        488.5                                                   Magnesium stearate     1.5                                                 (e) Injection I            (50 mg/ml)                                              Compound X              5.0% w/v                                               1M Sodium hydroxide solution                                                                          15.0% v/v                                               (to adjust pH to 7.6)                                                          Polyethylene glycol 400                                                                               4.5% w/v                                                Water for injection to 100%                                                (f) Injection II           (10 mg/ml)                                              Compound X             1.0% w/v                                                Sodium phosphate BP     3.6% w/v                                               0.1M Sodium hydroxide solution                                                                        15.0% v/v                                               Water for injection to 100%                                                                           (1 mg/ml,                                           (g) Injection III          buffered to pH 6)                                       Compound X              0.1% w/v                                               Sodium phosphate BP    2.26% w/v                                               Citric acid            0.38% w/v                                               Polyethylene glycol 400                                                                                3.5% w/v                                               Water for injection to 100%                                                                           mg/ml                                               (h) Aerosol I                                                                      Compound X             10.0                                                    Sorbitan trioleate     13.5                                                    Trichlorofluoromethane 910.0                                                   Dichlorodifluoromethane                                                                               490.0                                               (i) Aerosol II                                                                     Compound X             0.2                                                     Sorbitan trioleate     0.27                                                    Trichlorofluoromethane 70.0                                                    Dichlorodifluoromethane                                                                               280.0                                                   Dichlorotetrafluoroethane                                                                             1094.0                                              (j) Aerosol III                                                                    Compound X             2.5                                                     Sorbitan trioleate     3.38                                                    Trichlorofluoromethane 67.5                                                    Dichlorodifluoromethane                                                                               1086.0                                                  Dichlorotetrafluoroethane                                                                             191.6                                               (k) Aerosol IV                                                                     Compound X             2.5                                                     Soya lecithin          2.7                                                     Trichlorofluoromethane 67.5                                                    Dichlorodifluoromethane                                                                               1086.0                                                  Dichlorotetrafluoroethane                                                                             191.6                                               ______________________________________                                    

Note

The above formulations may be obtained by conventional procedures well known in the pharmaceutical art. The tablets (a)-(c) may be enteric coated by conventional means, for example to provide a coating of cellulose acetate phthalate. The aerosol formulations (h)-(k) may be used in conjunction with standard, metered dose aerosol dispensers, and the suspending agents sorbitan trioleate and soya lecithin may be replaced by an alternative suspending agent such as sorbitan monooleate, sorbitan sesquioleate, polysorbate 80, polyglycerol oleate or oleic acid. ##STR8## 

We claim:
 1. A hydroxylamine derivative of the formula Iwherein R⁴ is hydrogen, carbamoyl, (1-4C)alkyl, (2-5C)alkanoyl, N-(1-4C)alkylcarbamoyl, N,N-di-(1-4C) alkylcarbamoyl, benzoyl or phenylsulphonyl and wherein the benzoyl or phenylsulphonyl group may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, (1-4C)alkyl and (1-4C)alkoxy; R⁵ is hydrogen, (1-4C)alkyl, (3-4C)alkenyl, (3-4C)alkynyl, and (2-5C) alkanoyl; R⁶ is hydrogen, (1-4C)alkyl, phenyl or phenyl-(1-4C)alkyl and wherein each phenyl group may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, (1-4C)alkyl and (1-4C) alkoxy; R⁷ is hydrogen or (1-4C) alkyl; Ar¹ is phenylene which may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, (1-4C)alkyl and (1-4C)alkoxy;wherein A¹ is a direct link to X¹ ; X¹ is thio, sulphinyl or sulphonyl; Ar² is phenylene, which may optionally bear one or two substituents selected from halogeno, cyano, trifluoromethyl, (1-4C) alkyl and (1-4C) alkoxy; R¹ is (1-4C)alkyl, (3-4C)alkenyl or (3-4C)alkynyl; and R² and R³ together form a group of the formula --A² --X² --A³ -- which together with the carbon atom to which A² and A³ are attached define a ring having 6 ring atoms, wherein each of A² and A³ is independently (1-3C)alkylene and X² is oxy, and which ring may optionally bear one or two substituents selected from hydroxy, (1-4C)alkyl and (1-4C)alkoxy;or a pharmaceutically-acceptable salt thereof.
 2. The hydroxylamine derivative of the formula I as claimed in claim 1 selected from:N-[4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-α-methylbenzyl}-O-methylhydroxylamine, O-acetyl-N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-.alpha.-methylbenzyl}acetohydroxamic acid or N-{4-[5-fluoro-3-(4-methoxytetrahydropyran-4-yl)phenylthio]-α-methylbenzyl}-N-hydroxyurea;or a pharmaceutically-acceptable salt thereof.
 3. A pharmaceutical composition which comprises a hydroxylamine derivative of the formula I, or a pharmaceutically-acceptable salt thereof, as claimed in any one of claims 1 and 2 in association with a pharmaceutically-acceptable diluent or carrier.
 4. A method of treating a disease or medical condition mediated alone or in part by one or more leukotrienes which comprises administering to a warm-blooded animal requiring such treatment an effective amount of a hydroxylamine derivative of the formula I, or a pharmaceutically-acceptable salt thereof, as claimed in any one of claims 1 and
 2. 5. A pharmaceutical composition which comprises a hydroxylamine derivative of the formula I, or a pharmaceutically-acceptable salt thereof, as claimed in any one of claims 1-4 in conjunction or admixture with a cyclooxygenase inhibitory non-steroidal anti-inflammatory agent, and a pharmaceutically-acceptable diluent or carrier.
 6. A hydroxylamine derivative of the formula I as claimed in claim 1 whereinR⁴ is hydrogen, carbamoyl, acetyl, propionyl, benzoyl or phenylsulphonyl and wherein said benzoyl or phenylsulphonyl group may optionally bear one substituent selected from fluoro, chloro, methyl and methoxy; R⁵ is hydrogen, methyl, ethyl, propyl, acetyl and propenyl; R⁶ is hydrogen, methyl, ethyl or phenyl and wherein said phenyl group may optionally bear one substituent selected from fluoro, chloro, methyl and methoxy; R⁷ is hydrogen; Ar¹ is 1,4-phenylene which may optionally bear one substituent selected from fluoro, chloro, methyl and methoxy; Ar¹ is a direct link to X¹ and X¹ is thio; Ar² is 1,3- or 1,4-phenylene which may optionally bear one or two substituents selected from fluoro, chloro, trifluoromethyl, methyl and methoxy; R¹ is methyl, ethyl or allyl; and R² and R³ together form a group of the formula --A² --X² --A³ -- which together with the carbon atoms to which A² and A³ are attached define a ring having 6 ring atoms, wherein each of A² and A³ is ethylene and X² is oxy, and which ring may optionally bear one or two substituents selected from methyl and ethyl;or a pharmaceutically-acceptable salt thereof.
 7. A hydroxylamine derivative of the formula I as claimed in claim 1 whereinR⁴ is hydrogen, carbamoyl, acetyl, benzoyl or phenylsulphonyl; R⁵ is hydrogen, methyl, ethyl or acetyl; R⁶ is hydrogen, methyl or ethyl; R⁷ is hydrogen; Ar¹ is 1,4-phenylene; A¹ is a direct link to X¹ ; X¹ is thio; Ar² is 1,3-phenylene which may optionally bear one or two substituents selected from fluoro and chloro; R¹ is methyl, ethyl or allyl; and R² and R³ together form a group of the formula --A² --X² --A³ -- which together with the carbon atom to which A2 and A3 are attached define a ring having 6 ring atoms, wherein each of A² and A³ is ethylene and X² is oxy, and which ring may optionally bear one or two methyl substituents; or a pharmaceutically-acceptable salt thereof.
 8. A hydroxylamine derivative of the formula I as claimed in claim 1 whereinR⁴ is hydrogen, carbamoyl, acetyl or phenylsulphonyl; R⁵ is hydrogen or methyl; R⁶ is methyl; R⁷ is hydrogen; Ar¹ is 1,4-phenylene; A¹ is a direct link to X¹ ; X¹ is thio; Ar² is 1,3-phenylene or 5-fluoro-1,3-phenylene R¹ is methyl; and R² and R³ together form a group of the formula --A² --X² --A³ -- which together with the carbon atom to which A² and A³ are attached define a ring having 6 ring atoms, wherein each of A² and A³ is ethylene and X² is oxy, and which ring may optionally bear a methyl substituent alpha to X² ;or a pharmaceutically-acceptable salt thereof.
 9. A method of treating an inflammatory or allergic condition mediated by one or more leukotrienes which comprises administering to a warm-blooded animal requiring such treatment an anti-inflammatory or anti-allergic effective amount of a hydroxylamine derivative of the formula I, or a pharmaceutically-acceptable salt thereof, as claimed in any one of claims 1-5. 